Hard carbon film, production method thereof, and sliding member

ABSTRACT

A hard carbon film formed on a substrate via an intermediate layer is made up of a diamond-like carbon layer and a graphite particle deposition layer formed on the diamond-like carbon layer. The I D /I G  of the graphite particle deposition layer that is a ratio of the integrated intensity I D  of a peak representing the D band and the integrated intensity I G  of a peak representing the G band that are obtained through the peak separation of the Raman spectrum based on the Raman spectroscopic analysis is 1 or less.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2005-361994 filed onDec. 15, 2005 including the specification, drawings and abstract isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a hard carbon film and a production methodthereof as well as a sliding member. More particularly, the inventionrelates to a hard carbon film that includes a diamond-like carbon layerand a production method thereof as well as a sliding member made up byforming the hard carbon film on a substrate surface. The hard carbonfilm and the sliding member in accordance with the invention can besuitably used, for example, in vehicular engine component parts such asvalve lifters, piston rings, piston skirts, etc.

2. Description of the Related Art

The diamond-like carbon, having high hardness and low frictioncoefficient, has come to be used as surface reforming films of varioussliding members, mechanical component parts, tools, magnetic disks, etc.

In order to cope with the recent fuel economy regulations regardingmotor vehicles, it is very important to develop a technology forreducing sliding resistance. Therefore, it has become a major task toreduce the sliding resistance in motor vehicle component parts and,particularly, engine component parts.

Japanese Patent Application Publication No. JP-A-2004-339564 discloses asliding member as follows. In this sliding member, an intermediate layerhaving a metal layer made of chrome, titanium or the like as a lowerlayer, and a mixture layer of metal and carbon as an upper layer islayered on a surface of the substrate. Besides, in the sliding member, adiamond-like carbon layer is formed on the intermediate layer, and asolid lubricant coating film made of molybdenum disulfide or the like isformed on the diamond-like carbon layer.

However, the aforementioned sliding member has a problem that, in aninitial period of use, a long time is needed before the frictioncoefficient declines and stabilizes at a low friction coefficient, thatis, the fitting property is insufficient. Causes of this are consideredbe that the solid lubricant coating film, forming the outermost surface,is less apt to be smoothed by sliding, and that the crystal structure ofthe solid lubricant coating film is less apt to change into a structureexcellent in lubricity.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a hard carbon film of highfitting property whose friction coefficient can be quickly declined bysliding in an initial period of use so as to stabilize at a low frictioncoefficient value in an early period, and a production method thereof aswell as a sliding member.

A first aspect of the invention relates to a hard carbon film thatincludes a diamond-like carbon layer (hereinafter, referred to as “DLClayer”) formed on a substrate directly or via an intermediate layer. Thehard carbon film includes a graphite particle deposition layer(hereinafter, referred to as “Gr particle deposition layer”) formed onthe DLC layer. An I_(D)/I_(G) of the Gr particle deposition layer thatis a ratio of the integrated intensity I_(D) of a peak representing a Dband and the integrated intensity I_(G) of a peak representing a G bandthat are obtained through the peak separation of the Raman spectrumbased on the Raman spectroscopic analysis is 1 or less.

According to the first aspect of the invention, both the DLC layer andthe Gr particle deposition layer improve the antiwear property, anddecline the friction coefficient. The formation method of the DLC layeris not particularly limited. This formation method may employ, forexample, an ionization vapor deposition technique, a plasma CVDtechnique, an ark ion plating technique, a sputtering technique, etc.Besides, the formation method of the Gr particle deposition layer mayemploy a sputtering technique. However, from the viewpoint of seekingsimplification of the production process, the sputtering technique maybe used to consecutively form the intermediate layer, the DLC layer andthe Gr particle deposition layer.

The thicknesses of the intermediate layer, the DLC layer and the Grparticle deposition layer are appropriately settable in accordance withthe usage of a component part to which the invention is applied. Forexample, the thickness of the intermediate layer is about 0.1 to 1.0 μm,and the thickness of the DLC layer is about 0.5 to 10 μm, and thethickness of the Gr particle deposition layer is about 0.5 to 5 μm.

Besides, as for the DLC layer and the Gr particle deposition layer, oneor more species of metals, such as Cr, Ti, Si, W, B, etc., may be addedthereto.

In the evaluation of the Gr particle deposition layer based on the Ramanspectrum, a spectrum that has a broad peak near 1500 cm⁻¹ and has aslight shoulder near 1400 cm⁻¹ is obtained. The peak separation throughthe curve fitting of this Raman spectrum using the Gaussian function andthe Lorenz function provides a peak representing the G band near 1550cm⁻¹, and a peak representing the D band near 1350 cm⁻¹. In the hardcarbon film in accordance with the first aspect of the invention, the Grparticle deposition layer is specified. The I_(D)/I_(G), that is, theratio between the integrated intensity I_(D) of the peak representingthe D band and the integrated intensity I_(G) of the peak representingthe G band, is 1 or less.

The measurement of the Raman spectrum by the Raman spectroscopicanalysis employs, for example, a microscopic laser Raman spectroscopicdevice (trade name “NRS-1000” by Nippon Bunko). In this case,measurement is performed in the following measurement condition: a laserwavelength of 532.20 nm, and a laser diameter of 1 μm.

The peak representing the G band results from a Gr structure in whichcarbon atoms are sp²-bonded. The peak representing the D band resultsfrom the sp³ bond and an amorphous structure.

Therefore, in the Gr particle deposition layer, lower I_(D)/I_(G) valuesmean correspondingly lower proportions of the amorphous structure to theGr structure. In other words, the lower the I_(D)/I_(G) of a Gr particledeposition layer, the closer to graphite it is. Therefore, in the hardcarbon coating film, a Gr particle deposition layer whose I_(D)/I_(G) is1 or less has a structure that is very close to that of graphite, andgreatly contributes to improvement in the fitting property.

Therefore, the hard carbon film as mentioned above is a film with highfitting property whose friction coefficient quickly declines due tosliding in an initial period of use, and stabilizes at a low frictioncoefficient level in an early period.

From the viewpoint of further improving the fitting property of the hardcarbon coating film in accordance with the first aspect of theinvention, the I_(D)/I_(G) may be 0.5 or less, and it is particularlygood if it is 0.1 or less.

The Gr particle deposition layer is a layer formed by depositing Grparticles.

In the hard carbon film, the hardness of the DLC layer may be 10 GPa(Hv1000 in the Vickers hardness) or higher.

If the hardness of the DLC layer is less than 10 GPa, it becomesdifficult to effectively improve the antiwear property of the entirehard carbon film. Besides, it becomes difficult to secure a strength ofthe entire hard carbon film. The hardness of the DLC layer may be 12 GPaor higher, and it is particularly good if it is 15 GPa. From theviewpoint of improving the antiwear property, the higher the hardness ofthe DLC layer in the hard carbon film is, the better it is. However, fora reason from the upper limit in the material property intrinsic to DLC,the hardness of the DLC layer has an upper limit of about 80 GPa.

Incidentally, for example, if the DLC layer is formed by a sputteringtechnique, the hardness of the DLC layer is appropriately settable byadjusting the bias voltage, the introduction amount of hydrocarbon, etc.

A second aspect of the invention relates to a production method of ahard carbon film in which a hard carbon film is formed on a substratedirectly or via an intermediate layer. This production method comprisesthe step of forming a DLC layer on the substrate or the intermediatelayer by sputtering a solid carbon target by exposure to a rare gasplasma while introducing a hydrocarbon gas (hereinafter, referred to as“DLC layer forming process”), and the step of forming a Gr particledeposition layer on the DLC layer by sputtering a solid carbon target byexposure to a rare gas plasma while introducing an amount of ahydrocarbon gas which makes a volume ratio of the hydrocarbon gas to atotal amount of a rare gas and the hydrocarbon gas equal to or less than0.5% (hereinafter, referred to as “Gr particle deposition layer formingprocess”).

According to the second aspect of the invention, the production methodcomprises the DLC layer forming process and the Gr particle depositionlayer forming process, and consecutively forms the DLC layer and the Grparticle deposition layer by the sputtering technique of exposing thesolid carbon target to a rare gas plasma. In addition, if theintermediate layer is formed, the intermediate layer may also be formedby the sputtering technique.

The kind of rare gas for generating the rare gas plasma is notparticularly limited. As for the kind of rare gas, a generally used gas,such as Ar (argon) or the like, may be adopted. Besides, the kind ofhydrocarbon gas used in the DLC layer forming process and the Grparticle deposition layer forming process is not particularly limitedeither. As for the kind of hydrocarbon gas, an appropriate one may beselected from methane, acetylene, ethylene, benzene, etc.

In the DLC layer forming process, the DLC layer is formed on thesubstrate or the intermediate layer by the sputtering technique ofexposing the solid carbon target to a rare gas plasma while introducinga hydrocarbon gas.

In the foregoing production method of the hard carbon film, the Grparticle deposition layer of which an I_(D)/I_(G) that is a ratiobetween an integrated intensity I_(D) of a peak representing a D bandand an integrated intensity I_(G) of a peak representing a G band thatare obtained through peak separation of a Raman spectrum based on aRaman spectroscopic analysis is 1 or less may be formed in the Grparticle deposition layer forming process.

In the foregoing production method of the hard carbon film, the Grparticle deposition layer may be formed without introducing thehydrocarbon gas in the Gr particle deposition layer forming process.

According to the production method of the hard carbon film, the Grparticle deposition layer can be formed by the sputtering technique.However, if sputtering is performed while a hydrocarbon gas is beingsupplied, the Gr particle deposition layer will containgas-decomposition carbon and gas-decomposition hydrogen that aredecomposition components of the hydrocarbon gas are. If the Gr particledeposition layer contains the gas-decomposition carbon as carbonaceouselement or the gas-decomposition hydrogen, the deposition of Grparticles is inhibited so that a good Gr particle deposition layercannot be formed. Therefore, the self-lubricity and the like inherent ingraphite are inhibited. Therefore, the less the content of thegas-decomposition carbon and the gas-decomposition hydrogen in the Grparticle deposition layer is, the better it is. It is particularly goodif the content is 0 at %, that is, if the Gr particle deposition layercontains no gas-decomposition carbon and no gas-decomposition hydrogen.

In the production method of the hard carbon film, the DLC layer whosehardness is 10 GPa or higher may be formed in the DLC layer formingprocess.

In the DLC layer forming process, it is advisable to appropriately setthe bias voltage applied to the substrate, the introduction amount ofhydrocarbon gas, etc. so that the hardness of the DLC layer formedbecomes 10 GPa or higher. From such a viewpoint, it is advisable thatthe bias voltage applied to the substrate be about 30 to 450V, and it isparticularly good if it is set at about 50 to 200V. Besides, it isadvisable that the volume ratio of the hydrocarbon gas to the totalamount of the rare gas and the hydrocarbon gas be about 0.5 to 20%, andit is particularly good if it is about 2 to 10%.

In the Gr particle deposition layer forming process, the amount of thehydrocarbon gas which makes the volume ratio of the hydrocarbon gas tothe total amount of the rare gas and the hydrocarbon gas equal to orless than 0.5% is introduced. By performing the sputtering technique ofexposing the solid carbon target to a rare gas plasma while introducingthe hydrocarbon gas, the Gr particle deposition layer is formed on theDLC layer.

If the volume ratio of the hydrocarbon gas in the Gr particle depositionlayer forming process exceeds 0.5%, the content of the gas-decompositioncarbon and the gas-decomposition hydrogen in the Gr particle depositionlayer formed becomes excessively large. Therefore, the fitting propertyor the antiwear property cannot not be favorably improved. Then, theless the volume ratio of the hydrocarbon gas in the Gr particledeposition layer forming process is, the better it is. This means thatit is most favorable that the volume ratio be 0%, that is, thehydrocarbon gas be not introduced in the Gr particle deposition layerforming process. It is particularly good if the Gr particle depositionlayer is formed in this manner.

If the volume ratio of the hydrocarbon gas in the Gr particle depositionlayer forming process is 0.5% or less, the Gr particle deposition layerof which the I_(D)/I_(G) that is the ratio of the integrated intensityI_(D) of the peak representing the D band and the integrated intensityI_(G) of the peak representing the G band that are obtained through peakseparation of the Raman spectrum based on the Raman spectroscopicanalysis is 1 or less can be formed.

A third aspect of the invention is a sliding member comprising asubstrate and the foregoing hard carbon film.

Therefore, according to the sliding member in accordance with the thirdaspect of the invention, the fitting property and the antiwear propertycan be favorably improved. Hence, this sliding member can be suitablyused, for example, in valve lifters, piston rings, and piston skirts asvehicular engine component parts.

The material of the substrate is not particularly limited, and may be aferrous material, a nonferrous material, or a ceramic. For example,steel materials, such as carbon steel or various alloy steels forferrous plates or mechanical structures, hardened steel, etc., cast ironmaterials, such as flake graphite cast iron, spheroidal graphite castiron, etc., or Al alloys, Mg alloys, etc., may be suitably used.

The intermediate layer is a layer for improving the adhesiveness betweenthe substrate and the hard carbon film, and may be formed on thesubstrate in accordance with need. The kind of the intermediate layer isnot particularly limited but may be appropriately selected in accordancewith the material of the substrate, as long as the intermediate layer isable to improve the adhesiveness between the substrate and the hardcarbon film. For example, the kind of the intermediate layer may be acombination of one or more species of metal elements such as Cr, Ti, Si,W, B, etc.

Besides, from the viewpoint of further improving the adhesivenessbetween the substrate and the hard carbon film, the intermediate layermay be constructed of a metal layer made of the aforementioned metalelement or elements, and a gradient mixture layer made of theaforementioned metal element or elements and carbon in which the ratiotherebetween is changed in a gradient fashion (such that the proportionof metal increases with approach to the metal layer).

The formation method for the intermediate layer is not particularlylimited, and may employ an ionization vapor deposition technique, aplasma CVD technique, an ark ion plating technique, a sputteringtechnique, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of theinvention will become apparent from the following description ofpreferred embodiments with reference to the accompanying drawings,wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a sectional view schematically showing a sliding member inaccordance with an example of the invention;

FIG. 2 is a diagram showing results of investigation of the frictioncoefficients and the fitting properties of sliding members in accordancewith Examples 1, 4 and Comparative Examples 2 to 4 through a frictionwear test;

FIG. 3 is a diagram showing results of investigation of the antiwearproperty of sliding members in accordance with Examples 1 to 3 andComparative Example 1 through a friction wear test; and

FIG. 4 is a diagram showing results of investigation of the antiwearproperty of sliding members in accordance with Example 1 and ComparativeExample 2 through a friction wear test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the invention will be further described in detail withreference to embodiments and examples. The invention is not limited tothese embodiments or examples.

EXAMPLE 1

A sliding member in accordance with this example shown in FIG. 1 isconstructed of a substrate 1, an intermediate layer 2 formed on thesubstrate 1, and a hard carbon film 3 formed on the intermediate layer2.

The substrate 1 is made of SUS440C whose surface roughness is 0.02 μmRa.

The intermediate layer 2 is constructed of a Cr (chrome) metal layer 4of 0.5 μm in thickness formed on the substrate 1, a Cr/C gradientmixture layer 5 of 0.3 μm in thickness formed on the Cr metal layer 4.As for the Cr/C gradient mixture layer 5, the ratio between Cr and Dchanges in a gradient fashion such that the proportion of C (carbon)gradually increases with approach from the Cr metal layer 4 to a DLClayer (described below) of the hard carbon film 3. Incidentally,although in the example of the invention, the intermediate layer 2 isformed on the substrate 1, it is not altogether necessary to form theintermediate layer 2.

The hard carbon film 3 is constructed of a DLC layer 6 of 1.0 μm inthickness formed on the Cr/C gradient mixture layer 5 of theintermediate layer 2, and a Gr particle deposition layer 7 of 0.2 μm inthickness formed on the DLC layer 6.

The hardness of the DLC layer 6 in the hard carbon film 3 was measuredand found to be 18 GPa (Hv1800).

Besides, with regard to the Gr particle deposition layer 7 in the hardcarbon film 3, the Raman spectrum was measured in the above-statedmeasurement condition through the use of a Raman spectroscopic device.The peak separation through the curve fitting of the obtained Ramanspectrum using the Gaussian function and the Lorenz function provides apeak that represents the G band near 1550 cm⁻¹, and a peak thatrepresents the D band near 1350 cm⁻¹. Then, the I_(D)/I_(G) that is theratio between the integrated intensity I_(D) of the peak representingthe D band and the integrated intensity I_(G) of the peak representingthe G band was 0.51 as shown in Table 1, which will be shown later.

The sliding member in accordance with the example having theaforementioned construction was produced as described below through anunbalance magnetron sputtering technique (hereinafter, referred to as“UBMS technique”) using a sputtering device (“UBMS202” by Kobe Seikosho)(not shown).

<Oxide Layer Removing Process>

First, a substrate 1, and a sheet of a graphite target and a sheet of aCr target as solid carbon targets were placed at their respectivepredetermined positions in a sputtering device. Then, the sputteringdevice was evacuated to 3.0×10⁻³ Pa. After the temperature of thesubstrate 1 was raised to 200° C., the substrate 1 surface was exposedto Ar plasma (Ar bombardment) to remove the oxide layer of the substrate1 surface.

<Intermediate Layer Forming Process>After that, while the Ar gas forplasma generation and a methane gas were flowed in the device at anintroduction amount of 190 ml/min and an introduction amount of 10ml/min, respectively, the Cr target was sputtered, whereby a Cr metallayer 4 was formed on the substrate 1. Then, the Cr target and thegraphite target were simultaneously sputtered so that the amounts ofsputter thereof were changed in a gradient fashion, whereby a Cr/Cgradient mixture layer 5 was formed on the Cr metal layer 4.

In this manner, an intermediate layer 2 made up of the Cr metal layer 4and the Cr/C gradient mixture layer 5 was formed on the substrate 1.

Incidentally, in this intermediate layer forming process, the biasvoltage applied to the substrate 1 was set at 100V.

Besides, the volume ratio of the methane gas to the total amount of theAr gas and the methane gas in this intermediate layer forming processand in a DLC layer forming process described below is 5%.

<DLC Layer Forming Process>

Furthermore, consecutively from the intermediate layer forming process,the graphite target was sputtered, whereby a DLC layer 6 was formed onthe intermediate layer 2.

<Gr Particle Deposition Layer Forming Process>

After the DLC layer 6 was formed, the introduction of the methane gasinto the device was stopped. While only the Ar gas was being flowed atan introduction amount of 200 ml/min, the graphite target was sputtered,whereby the Gr particle deposition layer 7 was formed on the DLC layer6.

In this manner, a hard carbon film 3 made up of the DLC layer 6 and theGr particle deposition layer 7 was formed on the intermediate layer 2.

Incidentally, in the DLC layer forming process and the Gr particledeposition layer forming process, the bias voltage applied to thesubstrate 1 was set at 100V.

Besides, the volume ratio of the Ar gas to the total amount of the Argas and the methane gas in the Gr particle deposition layer formingprocess in this example is 0% as shown in Table 1, which will be shownbelow.

EXAMPLE 2

With regard to a sliding member in accordance with Example 2 of theinvention, the bias voltage applied to the substrate 1 in the DLC layerforming process is altered to 80V. Except for this process, the slidingmember is obtained by substantially the same method as in Example 1.

The hardness of the DLC layer 6 in this sliding member is 15 GPa(Hv1500).

EXAMPLE 3

With regard to a sliding member in accordance with Example 3 of theinvention, the bias voltage applied to the substrate 1 in the DLC layerforming process is altered to 65V. Except for this process, the slidingmember is obtained by substantially the same method as in Example 1.

The hardness of the DLC layer 6 in this sliding member is 12 GPa(Hv1200).

EXAMPLE 4

With regard to a sliding member in accordance with Example 4 of theinvention, in the Gr particle deposition layer forming process, while Arand the methane gas are flowed in the device at an introduction amountof 199 ml/min and an introduction amount of 1 ml/min, respectively, thegraphite target is sputtered, whereby a Gr particle deposition layer 7is formed. Except for this process, the sliding member is obtained bysubstantially the same method as in Example 1.

Incidentally, the volume ratio of the Ar gas to the total amount of theAr gas and the methane gas in the Gr particle deposition layer formingprocess of this example is 0.5%.

Besides, as for the Gr particle deposition layer 7 of the hard carbonfilm 3 in accordance with Example 4, the I_(D)/I_(G) is 0.99.

COMPARATIVE EXAMPLE 1

With regard to a sliding member in accordance with Comparative Example1, the bias voltage applied to the substrate 1 in the DLC layer formingprocess is altered to 50V. Except for this process, the sliding memberis obtained by substantially the same method as in Example 1.

Incidentally, the hardness of the DLC layer 6 in this sliding member is9 GPa (Hv900).

COMPARATIVE EXAMPLE 2

With regard to the sliding member in accordance with Comparative Example2, the Gr particle deposition layer forming process is not carried out.Except for this process, the sliding member is obtained by substantiallythe same method as in Example 1.

This sliding member is constructed of a substrate 1, an intermediatelayer 2 formed on the substrate 1 and made up of a Cr metal layer 4 anda Cr/C gradient mixture layer 5, and a hard carbon film formed on theintermediate layer 2 and made up only of a DLC layer 6.

COMPARATIVE EXAMPLE 3

With regard to a sliding member in accordance with Comparative Example3, in the Gr particle deposition layer forming process, while Ar and amethane gas are being flowed in the device at an introduction amount of195 ml/min and an introduction amount of 5 ml/min, respectively, thegraphite target was sputtered, whereby a Gr particle deposition layer 7is formed. Except for this process, the sliding member is obtained bysubstantially the same method as in Example 1.

Incidentally, the volume ratio of the Ar gas to the total amount of theAr gas and the methane gas in the Gr particle deposition layer formingprocess of this comparative example is 2.5%.

Besides, as for the Gr particle deposition layer 7 of the hard carbonfilm in accordance with Comparative Example 3, the I_(D)/I_(G) is 2.11.

COMPARATIVE EXAMPLE 4

With regard to a sliding member in accordance with Comparative Example4, in the Gr particle deposition layer forming process, while Ar and amethane gas are being flowed in the device at an introduction amount of197.5 ml/min and an introduction amount of 2.5 ml/min, respectively, thegraphite target is sputtered, whereby a Gr particle deposition layer 7is formed. Except for this process, the sliding member is obtained bysubstantially the same method as in Example 1.

Incidentally, the volume ratio of the Ar to the total amount of the Argas and the methane gas in the Gr particle deposition layer formingprocess of this example is 1.25%.

Besides, as for the Gr particle deposition layer 7 of the hard carbonfilm in accordance with Comparative Example 4, the I_(D)/I_(G) is 1.17.TABLE 1 Volume ratio of Ar (%) I_(D)/I_(G) Example 1 0 0.51 Example 40.5 0.99 Comparative Example 3 2.5 2.11 Comparative Example 4 1.25 1.17

(Friction Coefficient and Fitting Property Evaluation—Influence of GrParticle Deposition Layer)

With respect to the sliding members of Examples 1, 4 and ComparativeExamples 2 to 4, a block-on-ring friction wear test (LFW-1 test) isperformed to evaluate the friction coefficient and the fitting propertythereof.

This friction wear test is performed in a condition where a standardring (SAE4620) for the LFW-1 test is used as an opponent ring, and wherewhile this opponent ring is half dipped in an oil bath (lubricating oil:a base oil of engine oil 5W-30; bath temperature: 80° C.), the opponentring is rotated at a rotation speed of 160 rpm (0.3 m/s), and where thehard carbon film of each sliding member is pressed against the rotatingring with a load P of 30 kg (320 MPa) for 30 minutes.

In addition, for comparison, substantially the same test is performedwith respect to a substrate 1 made of SUS440C.

As shown by results of the test in FIG. 2, the sliding members ofExamples 1 and 4, each having a Gr particle deposition layer 7 whoseI_(D)/I_(G) is 1 or less, are excellent in the fitting property, andexhibit early decline of the friction coefficient. A reason for this isconsidered to be that the Gr particle deposition layer 7 whoseI_(D)/I_(G) is 1 or less is apt to become smoothed by sliding, and isapt to change into a crystal structure that is excellent in lubricity.

On the other hand, the sliding members of Comparative Examples 3 and 4,each having a Gr particle deposition layer 7 whose I_(D)/I_(G) exceeds1, are poor in fitting property, and bring about results substantiallythe same as the results of the sliding member of Comparative Example 2that does not have a Gr particle deposition layer 7. A reason for thisis considered to be that the mixing-in of the gas-decomposition carbonand the gas-decomposition hydrogen inhibited the deposition of graphite,and the smoothing by sliding and the change into a crystal structureexcellent in lubricity became less likely to occur.

Therefore, it can be understood that by reducing the I_(D)/I_(G) of theGr particle deposition layer 7 to or less 1, the fitting property of thehard carbon film 3 can be effectively improved.

(Antiwear Property Evaluation—Influence of Hardness of DLC Layer)

With respect to the sliding members of Examples 1 to 3 and ComparativeExample 1, the aforementioned block-on-ring friction wear test (LFW-1test) is performed to evaluate the antiwear property thereof.

Results of measurement of the wear depths after the end of the test areshown in FIG. 3.

As is apparent from FIG. 3, as for each of the sliding members ofExamples 1 to 3, the hardness of the DLC layer 6 is 10 GPa or greater.In each of the sliding members, the wear depth is only about 0.1 μm orless, and the antiwear property is remarkably improved.

On the other hand, as for the sliding member of Comparative Example 1,the hardness of the DLC layer is 9 GPa. The wear depth of this slidingmember is 1.2 μm. A reason for this is considered to be that since thehardness of the DLC layer 6 is low, the insufficient strength of the DLClayer 6 declines the antiwear property of the entire film.

Therefore, it can be understood that by making the hardness of the DLClayer 6 equal to or greater than 10 GPa, the antiwear property of thehard carbon film 3 can be effectively improved.

(Antiwear Property Evaluation—Influence of Gr Particle Deposition Layer)

With respect to the sliding members of Example 1 and Comparative Example2, the block-on-ring friction wear test (LFW-1 test) is performed whilethe load P is variously altered as follows: P=30 kg (320 MPa), 60 kg(420 MPa), 120 kg (600 MPa), whereby the antiwear property thereof isevaluated. Results of the test are shown in FIG. 4.

As is apparent from FIG. 4, by forming a Gr particle deposition layer 7whose I_(D)/I_(G) is 1 or less, the antiwear property can be improvedand, in particular, the antiwear property under high surface pressurecan be remarkably improved. This is also considered to be caused by thecrystal structure of the Gr particle deposition layer 7. Specifically,the Gr particle deposition layer 7 whose I_(D)/I_(G) is 1 or less is aptto become smoothed by sliding, and is apt to change into a crystalstructure that is excellent in lubricity. Besides this, due to aself-regeneration function, the Gr particle deposition layer 7regenerates and maintains such a structure. Therefore, it is consideredthat the impact of sliding can be absorbed and the propagation thereofto the DLC layer 6 can be restrained, and that therefore the antiwearproperty in the whole hard carbon film 3 will improve.

These results conclude that the hard carbon film 3 made up of the DLClayer 6 whose hardness is 10 GPa or higher and the Gr particledeposition layer 7 whose I_(D)/I_(G) is 1 or less will achieve improvedfitting property and improved antiwear property and reduced frictioncoefficient.

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments or constructions. To the contrary,the invention is intended to cover various modifications and equivalentarrangements. In addition, while the various elements of the preferredembodiments are shown in various combinations and configurations, whichare exemplary, other combinations and configurations, including more,less or only a single element, are also within the spirit and scope ofthe invention.

1. A hard carbon film comprising: a diamond-like carbon layer formed ona substrate directly or via an intermediate layer; and a graphiteparticle deposition layer which is formed on the diamond-like carbonlayer and of which an I_(D)/I_(G) that is a ratio of an integratedintensity I_(D) of a peak representing a D band and an integratedintensity I_(G) of a peak representing a G band that are obtainedthrough peak separation of a Raman spectrum based on a Ramanspectroscopic analysis is 1 or less.
 2. The hard carbon film accordingto claim 1, wherein a hardness of the diamond-like carbon layer is 10GPa or greater.
 3. A production method of a hard carbon film,comprising: forming a diamond-like carbon layer on a substrate or on anintermediate layer by sputtering a solid carbon target by exposure to arare gas plasma while introducing a hydrocarbon gas; and forming agraphite particle deposition layer on the diamond-like carbon layer bysputtering a solid carbon target by exposure to a rare gas plasma whileintroducing an amount of a hydrocarbon gas which makes a volume ratio ofthe hydrocarbon gas to a total amount of a rare gas and the hydrocarbongas equal to or less than 0.5%.
 4. The production method of the hardcarbon film according to claim 3, wherein an I_(D)/I_(G) of the graphiteparticle deposition layer that is a ratio of an integrated intensityI_(D) of a peak representing a D band and an integrated intensity I_(G)of a peak representing a G band that are obtained through peakseparation of a Raman spectrum based on a Raman spectroscopic analysisis 1 or less.
 5. The production method of the hard carbon film accordingto claim 3, wherein the graphite particle deposition layer is formedwithout introducing the hydrocarbon gas.
 6. The production method of thehard carbon film according to claim 3, wherein a hardness of thediamond-like carbon layer is 10 GPa or greater.
 7. A sliding membercomprising: the substrate; and a hard carbon film according to claim 1.